Circularly polarized luminescence and coordination geometries in mononuclear lanthanide(III) complexes

Two chiral lanthanide PrIII and HoIII complexes: NIR luminescence and nonlinear optical properties

“…It is well recognized that β-diketones are ideal ‘antenna’ ligands for sensitizing the emissions of Pr III and Ho III ions in the NIR region. 12–16 In particular, introducing chirality into luminescent Ln III complexes enables them to show some additional unique properties, such as circularly polarized luminescence, 18–26 ferroelectricity 27,28 and second-harmonic generation (SHG), 24,25 which are only observed in noncentrosymmetric (NCS) molecular assemblies. However, the reported chiral Ln III complexes with NIR luminescence are still limited mainly due to the fact that Ln III ions often have high coordination numbers (usually 7–10), which increases the difficulty of chiral control in such an emission system, and the use of enantiopure chiral ligands has proven to be the most effective strategy for acquiring chiral Ln III complexes.…”